To obtain a water-absorbent resin which has an improved vol. efficiency and can be industrially produced by cross-linking polysuccinimide with a polyamine and hydrolyzing residual unreacted imide rings.
Polysuccinimide, usually prepd. by the condensation by dehydration of aspartic acid, is treated with a condensing agent (e.g. dicyclohexylcarbodiimide) to give higher-mol.-wt. polysuccinimide, which is reacted with 0.1-40mol% (based on the total amt. of monomer units constituting the polysuccinimide) polyamine (e.g. an aliph., alicyclic, or arom. polyamine or amino acid having amino groups at the side chains or its deriv.) in an org. solvent at 20-50°C. The resultant partially cross-linked polymer is isolated from the reaction system by recrystallization, reprecipitation, and filtration and is then subjected to the hydrolysis of the imide rings remaining in the polymer. The hydrolysis is performed by adding an aq. alkali soln. to a suspension of the isolated cross-linked polymer in a homogeneous mixture of or a heterogeneous dispersion of water and an org. solvent.
TAMAYA HIROAKI
NAGATOMO AKINORI
